The present invention relates to a clasping device for clasping or fastening a flexible strap to hold an object firmly in position.
The U.S. Pat. No. 2,825,109, patented on Mar. 4, 1958, discloses a clasping device or buckle of a type comprising a substantially elongated frame having one end pivotally connected to a tongue or lever having a handle portion defined at one end thereof remote from the pivotal connection between the frame and the tongue. The tongue is comprised of a pair of opposed side members which are joined at the handle portion by a cross plate and at the other end by an end cross bar and an intermediate cross bar extending in spaced and parallel relation to the end cross bar. All of these elements constituting the tongue are shown to be integrally formed with each other and, for this purpose, it is obvious that the tongue is prepared from a single plate member of substantially rectangular shape by means of any known press work. In the tongue so constructed, the cross plate, end cross bar and intermediate cross bar are so positioned relative to the side members that joints between the opposed ends of any one of the cross plate, end cross bar and intermediate cross bar and respective edges of the side members provide a line or right-angled bend while the cross plate, end cross bar and intermediate cross bar lay on the same plane perpendicular to the respective edges of the side members.
As is the case with the tongue, the frame is comprised of a pair of opposed side members spaced a distance slightly greater than the distance between the side members of the tongue and connected to each other by means of a bridge member. The bridge member is so designed as to provide a retaining means for securing one end of the strap to the frame.
In the clasping device or buckle of the above mentioned U.S. patent, a portion of the strap adjacent the other end thereof is adapted, when the tongue is in a folded or released position over the frame and with the side members thereof adjacent the side members of the frame, to pass below the cross bars of the tongue, thence over the intermediate cross bar and back through a clearance between the cross bars and then below the end cross bar in contact with the body portion of the strap to form a loop around the intermediate cross bar. With this clasping device or buckle, when the strap is drawn taut as the tongue is pivoted towards a fastened position through the frame and into substantially the same plane as said frame, a double width of the strap, defined by an overlap of one portion of the strap over another portion of the same strap, is presented over the end cross bar to provide substantial frictional resistance to relative movement of the strap loop after the strap is tightened by pivoting of the tongue within the frame.
Although the prior art clasping device of the above described construction has been found to be an instrument convenient to temporarily hold packages together and to readily release them from each other. However, it has been found that the prior art clasping device has some disadvantages. By way of example, after the tongue has been pivoted to a substantially intermediate position between the released and fastened positions by the application of an external drawing force thereto during a fastening operation, an external pulling force applied to the other end of the flexible strap to held the strap taut temporarily no longer acts on a major portion of the flexible strap encircling the object to be held in position. This is because said one portion of the strap tightly presses said another portion of the same strap against the end cross bar to substantially avoid the relative movement of the strap loop around the intermediate cross bar.
In addition, when the tongue is pivoted to the fastened position, the handle portion of the tongue is held flat against and in contact with a portion of the strap emerging outwardly from the tongue and held under tension, which portion is accommodated within a space between the side members of the tongue. This means that, while the pivotal movement of the tongue from the released position towards the fastened position is satisfactory, the return movement of the tongue from the fastened position back towards the released position cannot readily be performed because there is no other way to hold the handle portion than to pull the free end of the strap in a direction required for the handle portion to separate away from the portion of the strap under tension. In most applications, not only is this procedure complicated, but also the hand of an operator grasping the free end of the strap in an attempt to move the handle portion away from the strap under tension to cause the tongue to pivot towards the released position tends to be wounded from a slip of the hand relative to the free end of the strap.
Moreover, when the prior art clasping device is not in use, the strap tends or is liable to separate or fall off from the clasping device with the free end of the strap released from the tongue. Even though the strap does not separate or fall off from the clasping device, subsequent fastening of the strap by pivoting the tongue towards the fastened position while the strap loop is considerably loosened often results in formation of one or more twists in the strap loop and/or in the major portion of the strap encircling the object to be firmly held in position.
In addition to or independently of the formation of the twist or twists, there is another possibility that the strap loop when loosened rides over the end of either one of the side members of the tongue to disengage from the end cross bar as the tongue is pivoted towards the fastened position during the fastening operation. Once the strap loop is disengaged from the intermediate cross bar after having ridden over the end of one of the side members of the tongue, the clasping device does not operate satisfactorily unless the position of the strap loop is corrected.